South Korea's ruling party chief said Sunday that she has made efforts to convince the US side to seek a peaceful solution to the North Korean nuclear crisis on the Korean Peninsula.

"During my trip to the United States, I emphasized two things," Choo Mi-ae of the Democratic Party told reporters upon arrival at Incheon International Airport. "The first one is to explain the heightened tensions surrounding the Korean Peninsula stemming from North Korea's nuclear crisis and call for a peaceful means to solve the issue."

Choo Mi-ae speaks to reporters upon arriving at the Incheon International Airport after a 6-day stay in the US. (Yonhap)

She returned to South Korea after a six-day visit to Washington and New York for meetings with US officials, lawmakers and scholars, as well as to attend various events.

"Also, I saw that the United States is firm with the Seoul-Washington alliance and will keep a security priority about South Korea under any circumstances," she added.

For the upcoming negotiations to amend the bilateral free trade agreement, Choo said she has called for the fair assessment of the deal before launching the talks.

"I stressed that both sides have to conduct a study on the bilateral trade pact and go to the negotiation table based on fair and reasonable arguments," she said. "I also asked them to seek win-win solutions for both countries."

Seoul and Washington recently began domestic procedures to amend the five-year-old free trade agreement, known as KORUS, due to President Donald Trump's insistence it has widened the US trade deficit with South Korea. (Yonhap)